JPS63174961A - Manufacture of polyisocyanate having burette structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improved method for producing polyisocyanates having a biuret structure.

[Conventional technology]

It is known to produce polyisocyanates with a biuret structure by reacting excess organic diisocyanates directly with organic diamines at elevated temperatures. For example, DE 2,261,065 (Example 16) discloses the reaction of an excess of 1,6-diacyanatohexane with 1,6-diamithexane, in which the reactants are Stir at 180°C for 12 hours. This intense heating at high temperatures is not only uneconomical, but also results in discoloration of the reaction product, especially under large scale manufacturing conditions. This limits the use of this product in non-fading lacquers. In fact, Example 16 of the German publication
Even after reprocessing, it was not possible to obtain a monomer-based diisocyanate-free biuret polyisocyanate free of any insoluble gel-like by-products.

In the process disclosed in DE 2,609,995, gaseous diamines are introduced into existing diisocyanates at temperatures of 100 DEG to 250 DEG C. No precipitation of polyurethane occurs during this step and the reaction mixture becomes a clear solution at all times. This is achieved by serial dilution of the diamine introduced in gaseous form. Although this method allows the production of high-valent polyisocyanates with a biuret structure, it is not suitable for implementation on an industrial scale because it requires large amounts of gaseous diamine and the reaction conditions have to be very tightly controlled. do not have.

EP 3,505 discloses a method for introducing diamines into existing diisocyanates under excess pressure using a smooth jet nozzle of defined dimensions.

Depending on the reaction temperature, reaction temperatures up to 250° C. can be used, a urea dispersion is formed in this prior art process in an excess of starting diisocyanate. A subsequent heat treatment converts this dispersion into a solution of biuret polyisocyanate in excess of starting diisocyanate.

One drawback of this method, besides requiring the use of special equipment (smooth jet nozzle), is that the resulting polyisocyanate with a biuret structure requires the removal of excess starting diisocyanate (particularly 1,6-diisocyanatehexane). The reason is that it subsequently contains a considerable proportion of higher oligomers and by-products. This leads to an increase in viscosity, an undesirable decrease in NGO content, as well as poor dilutability towards co-solvents.

[Key points of the invention]

It has now been found that it is possible to produce high-valent polyisocyanates with a biuret structure based on aliphatic or cycloaliphatic diisocyanates or diamines without using special mixing equipment. This is achieved if the starting materials are reacted with each other at temperatures above 250°C, preferably above 270°C. This finding supports the accepted wisdom that reaction temperatures higher than 250°C should be avoided as much as possible to prevent undesirable discoloration of the reaction products.
See for example German Publication No. 2.609.995]
This is especially surprising in light of this.

The present invention utilizes an excess amount of an organic diisocyanate having exclusively aliphatic and/or cycloaliphatically bonded isocyanate groups to
Continuous reaction at elevated temperatures with organic diamines having 7-mino groups allows the continuous production of polyisocyanates with a biuret structure - in this method the reactants are reacted at temperatures above 250 °C. .

The present invention relates to a method for producing polyisocyanate having a biuret structure. In this method, excess organic diisocyanate having aliphatic and/or cycloaliphatically bonded isocyanate groups is mixed with an organic diamine having aliphatic and/or cycloaliphatically bonded amino groups.
The reaction is carried out at a temperature higher than 0°C.

The starting materials for the process of the invention are organic diisocyanates having exclusively aliphatic and/or cycloaliphatically bonded isocyanate groups with a molecular weight of less than 300.

Examples of diisocyanates of this type are 1,4-diisocyanato-butane, 1,6-dicyana[hexane, 1,6
-diisocyanato 2,2.4-)limethyl-hexane, 1,6-diisocyanato 2.4.4-1-limethylhexane, 2,6-diisocyanatocabroic acid ethyl ester, l,12- Diisocyanatododecane, 1.4
-diisocyanatocyclohexane, 1-isocyanato-
Includes 3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 4,4'-diisocyanatodicyclohexylmethane and 6-isocyanatocabroic acid-2-isocyanatoethyl ester. Any mixtures of these diisocyanates can also be used. Particularly suitable is 1,6-diisocyanatohexane.

The organic diamine starting material for the process of the invention is 300
organic diamines having exclusively aliphatic and/or cycloaliphatically bonded 17th amino groups having a molecular weight of less than Examples are 1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane, 1,6-diamino-2,2,4-trimethyl. Hexane, 1,6-diami2,4,4-trimethylhexane, 1,4-diaminohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane and 1,4,4-
Includes diamino-dicyclohexylmethane. Any mixtures of these diamines can also be used. Particularly suitable is 1,6-diaminohexane.

In the process of the invention, the diamine can also be used in admixture with water and/or a polyhydric aliphatic alcohol having a molecular weight of less than 500. Glycol, 1,6-cyhydroxy-hexane, 1,3-dihydroxy-2-ethyl-hexane, 1,6-cyhydroxy-2.2.4-)limethylhexane, 1,6-cyhydroxy-2.4.4- These include trimethylhexane, trimethylolpropane, glycerin, and short chain hydroxy-functional polyethers of simple polyols of this type with a minor amount of aliphatic dicarboxylic acids such as adipic acid, succinic acid and azelaic acid. Polycabraftones with low molecular weight hydroxyl groups starting from the simple polyols mentioned in these examples are also passed.

Any mixtures of these polyhydric alcohols can also be used.

However, the simultaneous use of water and/or polyhydric alcohols is undesirable; if additional starting materials of this kind are used, these can be used in amounts of up to 0.2 mol of water per mole of diamine and/or up to 1 mol of water per mole of diamine. , preferably in an amount of 0.5 mol of polyhydric alcohol.

In the process of the invention, the starting diisocyanate and the diamine or the mixture of the diamine and the water and/or the polyhydric alcohol have a ratio of isocyanate groups to amino groups of at least 4:1 to 25:1, particularly preferably 7:1 to 20:1. The primary amino groups are considered as monovalent groups for the purpose of calculations of this type.

The present invention involves combining the starting materials with each other at a temperature above 250°C, preferably above 270°C, especially immediately after thorough mixing.
It is essential to react at a temperature between 320°C. High reaction temperatures at the start of these reactions can be achieved by preheating the diisocyanate to a temperature above 180°C, preferably above 220°C. If a large excess of diisocyanate is used, preheating of the diamine or the mixture of diamine and water and/or polyhydric alcohol is often unnecessary.

However, generally diamines or mixtures of diamines with water and/or polyhydric alcohols have a
Preheated to ℃. Generally, it is expected that the reaction mixture will heat to a temperature of about 20-70° C. higher than would be expected due to heating of the starting materials without heating the mixing vessel.

This is because a high heat of reaction is generated due to the reaction that occurs temporarily.
kcal/kg K) and reaction enthalpy (approximately 3
5 kcal, 11 mol).

Furthermore, these can also be determined by simple preliminary experiments if necessary.

Heating of the diisocyanate should take place within as short a time as possible, preferably within 30 seconds. This is because these compounds are known to be temperature sensitive. This rapid heating can be achieved using conventional heat exchange equipment in the prior art. Heat exchangers useful in practicing the invention include shell-and-tube exchangers, bundle exchangers, and plate-type exchangers. These use heated water vapor with a fluid heating medium,
Alternatively, this can be done by direct electrical heating. 3
Particular preference is given to using a heat exchanger which is capable of heat-treating the initial diisocyanate within a time of up to a second.

In the process of the present invention, in which a continuous stream of reactants is mixed in a mixing chamber after preheating, there are no special requirements on the volume of the mixing chamber with respect to intensive mixing of the components, as known to those skilled in the art. Static or dynamic devices can be used.

In general, a simple reaction tube without baffles, with direct contact of the reaction components at one end, is sufficient, and is also preferred.

The point of introduction of the components is preferably in the form of a perforated screen or nozzle, the introduction of which can take place under elevated pressure. Measures of this kind ensure that the reaction mixture does not reach the feed of diisocyanate and diamine. For this purpose the cross-sectional area is in each case between 1.5 and 100 bar, preferably between 1.5 and 4 bar.
A pressure of 0 bar is selected. The form and arrangement of the nozzle and/or perforated screen and the high pressure are not essential to the invention.

the volume of the mixing chamber and any cooling areas or chambers;
and the intensity of the cooling in the cooling zone or chamber such that the average residence time for reducing the reaction mixture consisting of the combination of starting components to a temperature below 250° C. is at most 60 seconds, preferably within 30 seconds, particularly preferably within 10 seconds. 0 In the method of the present invention, 2 must be selected so that 2
The average residence time of the reaction mixture at suitable temperatures above 70° C. is generally at most 20 seconds, preferably at most 10 seconds, particularly preferably at most 1 second.

After passing through the mixing chamber and all cooling zones or chambers, the reaction mixture is heated gradually or stepwise to 80-220°C (preferably 120-220°C) within a maximum of 10 minutes, preferably within a maximum of 5 minutes, in a suitable heat exchanger. 200°C) and then thermal after-treatment at this temperature in a suitable post-reactor for a residence time of preferably up to 5 hours, more preferably up to 2 hours, particularly preferably up to 30 minutes. It is essential that the reaction mixture carried out is subjected to a temperature above 250° C. only within the short time mentioned above. However, the time of thermal post-treatment can vary within a wide range. Generally, at lower temperatures in the temperature range of 80-220<0>C, relatively long-lasting thermal post-treatments are desired; at higher temperatures, relatively short thermal post-treatments are desired.

Thermal aftertreatment can be carried out, for example, in reactors arranged in a cascade or in stirred vessels with continuous flow.

After the thermal work-up, the reaction product is present as a solution of the polyisocyanate containing biuret groups in an excess of the starting diisocyanate. Immediately after thermal post-treatment, this solution
Alternatively, excess starting diisocyanate can be removed by distillation or at a later point, for example by extraction with n-hexane. In this way, high valence polyisocyanates with a biuret structure can be obtained, with a maximum content of excess starting diisocyanate of 0.
7% by weight, preferably 0.3% by weight.

The polyisocyanates having biuret groups prepared by the process of the invention, in particular the polyisocyanates prepared exclusively by using 1,6-diisocyanatohexane and 1,6-diamino-hexane as starting materials, are It serves as a valuable starting material for producing component polyurethane lacquers.

The products of the invention are characterized by their good color value, good dilutability to cosolvents and relatively low viscosity.

The use of water and especially low molecular weight polyhydric alcohols such as those mentioned above to incorporate urethane or allophanate groups into the product improves the flexibility, bonding properties and hydrolytic stability of polyisocyanates and coatings produced therefrom. It becomes possible to modify the hardness and/or solvent stability.

〔Example〕

The invention will now be further illustrated by examples, in which all percentages are by weight.

In each of the following examples, the apparatus shown in FIG. 1 was used.

In FIG. 1, the reference symbols indicate: 1 indicates the diisocyanate stirred vessel, 2 indicates the diisocyanate feed pump, 3 indicates the diamine stirred vessel, 4 indicates the diamine feed pump, 5 indicates a co-solvent stirring vessel, 6 indicates a co-solvent supply pump, 7 indicates a heat exchanger for heating the diamine and co-solvent, and 8 indicates a heat exchanger for heating the diisocyanate. 9 indicates a mixing chamber, 10 indicates a heat exchanger for cooling the reaction mixture, and 11 indicates an impeller type mixer for the product of the process.

The co-solvent (for example diphenyl ether from vessel 5) is used only at the start of operation in a continuous drive and is introduced together with the diisocyanate into the mixing chamber to create constant temperature conditions, which causes a back-up of the components in the feed stream. This means ensuring that no mixing occurs. Actual start-up of the device was accomplished simply and safely by switching the solvent flow to the diamine stream. A nozzle was provided before the inlet of the diisocyanate and diamine flow into the mixing chamber to achieve high flow rates at this point. In principle, the shapes of these nozzles can be freely selected.

This is because these nozzles do not have the role of introducing mixing chamber energy into the reaction solution, but only have the role of reliably preventing back-mixing.

Immediately after exiting the mixing chamber, the reaction mixture is transferred to a heat exchanger 10.
Thermal after-treatment of the reaction product, which had been cooled to a low temperature level within the residence times given in the examples, was carried out in an impeller-type mixer 11 with continuous inlet and outlet flow. Such after-treatment could also be carried out in a stirred pot cascade or in a correspondingly sized retention area.

As stirring containers 1, 3.5 and 11, glass containers were used. Pump 2 the piston injection pump (LEWA)
．． 4 and 6.

Double pipe heat exchangers are used as heat exchangers 7 and 8, which are driven by oil as heat transfer medium, with an internal capacity of the near heat exchanger having the following dimensions: 22.8 cd 0.4
CD heat exchanger surface area 415 cj 31
．． 5cd With these dimensions, the desired short residence time at high temperature was achieved.

The mixing chamber 9 was formed as a cylindrical pipe with a nozzle opening of 0.1 mm in diameter for the diamine and two nozzle openings of 0.5 mm in diameter for the diisocyanate at the inlet, with a length of 5 cm x 4 m + w. given the dimensions.

The heat exchanger 1O, which has a volume of 0.6 and is connected directly to the mixing chamber, can also be a pipe-type heat exchanger with variable volume, and the different sections can be adjusted in different ways. The exact conditions are shown separately in the individual examples.

1.6-diisocyanato-hexane (HDI) and 1.6-diisocyanato-hexane (HDI)
-diamithexane (HD^) was introduced into vessels 1 and 3 at 70°C. No diphenyl ether.

The active solvent was likewise introduced into container 5 at approximately 70°C. HDI of 338 g/sin for 15 minutes and 2
After heating 0.0 g/sin of cosolvent (instead of HflA) to a temperature of 240 °C (1101) and 190 °C (cosolvent) via heat exchangers 7 and 8 and introducing it into the mixing chamber. , the inflow of co-solvent was blocked.

HDI of 20.3 kg/h (=120.8 mol/h
) is heated to 240°C (HD
and heated to a temperature of 190°C (1(1)A),
These were introduced into the mixing chamber. The temperature of the mixing chamber was adjusted to 285°C.

The average residence time at this temperature from the inlet of the feed main into the mixing chamber to the inlet into the heat exchanger 10 was approximately 0.5 seconds 6 It then exits the mixing chamber at a temperature of 285°C. The reaction mixture was cooled to 140°C in a heat exchanger 10. The average residence time in this heat exchanger was 4 minutes. The time from entering the condenser 10 to the temperature dropping to 250° C. was approximately 4 seconds. The reaction mixture was then stirred in a stirred vessel 1 at 140° C. for an average residence time of 1 hour. did. The process product (21,48 kt/h) continuously flowing out of the stirred vessel 11 had an NGO content of 39.4%. Excess [
After removing 0 to a residual content of 0.3%, the crude solution 1
A polyisocyanate with 357 g/kg of biuret groups was obtained, the properties of which were as follows: NGO content 22.7% Viscosity (23° C.) 5870 mPa5AP
HA color value 70-90 ±-
1 Using the same procedure as described in Example 1, 21.2 fur
/h (・126 mol/h) of 1101 is 0.812 k
g/h (-7.0 mol/h) of HDA, i.e. at a molar ratio of 18:1) was reacted under the following conditions: Temperature of MDI before reaction: 260°C Pre-reaction A Temperature: 140℃ Temperature in mixing chamber:
Average residence time at 290°C: 20.5 seconds After exiting the mixing chamber, this mixture was
It cools down to 160°C within minutes, where the time (average residence time) from the point of entry into the cooler 10 to the point of reduction to the temperature of 250°C is about 4 seconds, and then further at this temperature. Stirred for 30 minutes.

22.12kr/ with 41.8% NCOi & growth
A “crude biuret solution” of h was obtained, which was 0.2%
After removing the excess 801 to a residual content of 280 g of polyisocyanate having the following properties, 1 k of the crude solution
Produced per g: NGO content ml 23.1%
Viscosity (23℃) 2450+wPa
sAPHA color value 110-130 large ■ - Using the same procedure as described in Main Example I, 19.2 kg/
h (-114,3 mol/h) of HDI to 1.33 k
r/h (-11,4 mol/h)), i.e. at a molar ratio of 10:1), the reaction was carried out under the following conditions:
Temperature of HDI before reaction = 220°C Temperature before reaction A before reaction: 160°C Temperature in mixing chamber: 278°C Average residence time at 278°C: 20.5 seconds The reaction mixture flowing out from the mixing chamber was
It was cooled to 120° C. within minutes and then stirred at this temperature for a further 4 hours. In this step, the time (average residence time) from the time when it entered the cooler 10 until the time when the temperature decreased to below 250° C. was 5 seconds.

20.53kr/h with 36.8% NGO content
A "crude biuret solution" was obtained. After removing excess HDI (up to a residual content of 0,1%), 460 g of polyisocyanate with the following properties are obtained in 1 kg of crude solution
Obtained per: NGO content 21.7% viscosity It(2
3℃) IO, 50OaPasAPHA
Color value: 60-70 Omune Mottari - Soil Using the procedure described in Example 1, 14.61 qt/h (
-86.9 mol/h) of Hall and 3 mol parts of IIDA
and 1 mole part of 2,2-dimethyl-propanediol-1
．． It was reacted with 1.07 kg/h of the mixture with 3 under the following conditions: Temperature of HDI before reaction: 24-3℃ Temperature of HDA/neopentyl glycol mixture before reaction:
Temperature in the 190°C mixing chamber:
272°C Average residence time at 272°C: approx. 0.7 seconds After exiting the mixing chamber, the mixture was cooled to 145°C within 3 minutes and then stirred at this temperature for a further approx. 30 minutes. In this process, the time (average residence time) from the point of entry into the cooler 10 to the point of temperature drop below 250° C. was about 4 seconds.

Crude solution 15.6 containing biuret groups, urethane groups and allophanate groups and having an NGO content of 35.8%
7 kg/h was obtained, which corresponds to 413 kg/h of excess I (after removing the DI) up to a residual content of 0.3% per lumen of the crude solution.
g of polyisocyanate, which had the following properties: NGO content 1 20.7% viscosity (23
℃) 18.900mPa5APHA
Color value: 180 Otsuchi Yutatsu Using the method described in Example 1, 5. Okg/
h (= 89.3 mol/h) of HDI in a mixture of 95 mol parts of 1 (DA and 5 mol parts of water 1.099 kg/h)
was reacted under the following conditions; Before reaction) HDI (7) Temperature: 240
℃Pre-reaction Pre-reaction A/)I□0 Temperature of mixture: 190
Temperature in mixing chamber: 295°C 290°C
Average residence temperature in °C: approx. 0.6 After exiting the paper joint, the mixture was cooled within 2 minutes to 160 °C and then stirred at this temperature for a further 15 minutes. In this process, from the point of entry into the cooler 10, 250
The time to drop below the temperature of 'C (average residence time) was about 6 seconds.

16.0 kg/h (with NGO content of 35.1%)
7) A “crude biuret solution” is obtained, 1 which after removing excess HDI to a residual content of 0.2% Ili
536 g of polyisocyanate was produced per kg of solution, which had the following properties: NGO content 21.3% viscosity (23
℃ 30. 000sPasAPHA
Color value: +10-130 or more Although the present invention has been described in detail for the purpose of explanation, the details are merely for the purpose of explanation, and it is understood that various modifications may be made without departing from the spirit and scope of the present invention. I hope the businesses will understand.

[Brief explanation of the drawing]

No. 11ffl is a schematic diagram of an apparatus useful for carrying out the method of the invention. 1- Stirring container 2... Pump 3...- Stirring container 4...- Pump 7.8-- Heat exchanger 9- Name of mixing room agent Kawahara 1)
-Ear FIG, 1

Claims (13)

[Claims] (1) (a) an excess amount of an organic diisocyanate having an aliphatic and/or alicyclically bonded isocyanate group; (b) an organic diamine having an aliphatic and/or alicyclically bonded primary amino group; and a method for producing a polyisocyanate having a biuret structure, characterized in that the reaction is carried out in a reactor at a temperature higher than 250°C. (2) The method according to claim 1, wherein the reaction is carried out continuously. (3) The method according to claim 1, wherein the reaction is carried out at a temperature higher than 270°C. (4) The method according to claim 1, wherein the reactants are present in the reactor for an average residence time of up to 60 seconds. (5) The method according to claim 3, wherein the reactants are present in the reactor for an average residence time of up to 60 seconds. (6) The method according to claim 1, wherein the organic diamine is used in combination with water and/or a polyhydric aliphatic alcohol having a molecular weight of less than 500. 7. Process according to claim 1, in which the organic diamine is used in admixture with up to 0.2 mol of water and/or up to 1 mol of polyhydric alcohol having a molecular weight below 500 per mol of diamine. (8) The method according to claim 1, wherein the organic diisocyanate is 1,6-diisocyanato-hexane. (9) The method according to claim 8, wherein the organic diamine is 1,6-diamino-hexane. (10) The method according to claim 1, wherein the organic diamine is 1,6-diamino-hexane. (11) Claim 1 further comprising cooling the reaction mixture to a temperature of 80 to 220°C within 10 minutes.
The method described in section. 12. The method of claim 11, further comprising: (12) removing unreacted diisocyanate (a) from the reaction mixture by distillation. 13. The method of claim 1, further comprising: (13) removing unreacted diisocyanate (a) from the reaction mixture by distillation.